Dried packaged convenience foods or mixes, such as, for example, soups, casseroles, salads, and the like, are popular. Such foods or mixes frequently contain various types of dehydrated vegetables (generally with water activities of less than about 0.5) along with other food components. Unfortunately, such dehydrated vegetables, when cooked, tend to rehydrate slowly, require long cooking times, and generally do not resemble fresh vegetables in terms of color, texture, and/or nutrition. In addition, dried vegetables tend to fracture easily during handling and distribution resulting in large amount of powdery fines and an undesirable, unnatural appearance. One of the alternatives to dried vegetables is infused or intermediate water activity vegetables by infusing blanched vegetable with a low-Aw infusion mixture and followed by drying the infused vegetable to an Aw below about 0.9, and more typically below about 0.6. The accumulated thermal effect during conventional infusion and subsequent drying steps, especially in presence of reducing sugars or other saccharides, renders significant quality loss in infused vegetables. The sugars and other saccharides used in conventional infused intermediate moisture vegetables also impart undesirable candy-like appearance and surface stickiness.
Numerous attempts have been made to prepare infused and/or dehydrated vegetables having improved properties. U.S. Pat. No. 3,623,893 (Nov. 30, 1971) used super-atmospheric pressures (i.e., 200 to 4000 psi) to infuse foods, including vegetables, with an aqueous infusion cocktail containing propylene glycol, potassium sorbate, glycerol, and salt. Of course, the use of such high pressures would involve high capital expense if such a system were used commercially.
U.S. Pat. No. 3,745,027 (Jul. 10, 1973) provided a method for cooking vegetables in an infusion mixture containing, for example, glycerol, salt, propylene glycol, potassium sorbate, and water. For example, diced carrots cooked for 15 minutes in the infusion mixture and then soaked for 6 hours in the infusion mixture were reported to have “acceptable eating qualities and microorganic stability.”
U.S. Pat. No. 4,832,969 (May 23, 1989) provides improved dried green vegetables using an infusion cocktail containing a polyhydric alcohol, a sugar, an alkaline buffering system or agent (i.e., sufficient to obtain a cocktail pH of about 6 to 8), an inorganic bittering agent (e.g., KCl and/or MgCl2), a surfactant, salt, and an anti-oxidant (e.g., vitamin E, tocopherol, BHA, BHT, or mixtures thereof). After treatment with the infusion cocktail, the vegetable pieces are dried to a water activity of about 0.3 to 0.85 at a temperature of less than about 135° F. The resulting dried green vegetables are reported to have superior color retention for extended time periods even at room temperature storage, superior texture upon rehydration, and excellent rehydration rates.
U.S. Pat. No. 4,946,693 (Aug. 7, 1990) provides a process for preparing intermediate moisture vegetables. In this process, vegetables are blanched or cooked, preferably using a microwave oven, and then partially dried (i.e., water content of 45 to 55 percent). The dried vegetables are then dry mixed with salt (and optionally sodium glutamate if the vegetables are not cooked using a microwave oven); an anti-mycotic agent can also be added.
U.S. Pat. No. 5,110,609 (May 5, 1992) provides a method for producing intermediate moisture vegetables wherein the vegetables are partially dehydrated to a moisture content of 26 to 60 percent and then stored in an oxygen free atmosphere.
U.S. Pat. No. 5,925,395 (Jul. 20, 1999) provides a method for preserving vegetables whereby the vegetables are treated with a preservative solution containing water, calcium ions, and optionally ascorbic acid or erythorbic acid. The resulting vegetables are then stored at a non-freezing temperature less than 20° C. If stored at ambient temperatures, microbial contamination is possible.
U.S. Pat. No. 6,159,527 (Dec. 12, 2000) provides a method and apparatus for infusing fruit, including vegetables, using an infusion cocktail containing sugar wherein the flowrate and infusion cocktail are controlled such that the fruit or vegetables are exposed to progressively higher concentrations of sugar of a level only sightly higher than the sugar content of the fruit or vegetables being infused.
More recently, U.S. Pat. No. 6,403,134 (Jun. 11, 2002) provides a method for preparing intermediate moisture vegetables by (a) infusing vegetables with an antimicrobial infusion cocktail at a temperature of greater than about 50° F. for about 15 to about 180 minutes, wherein the antimicrobial infusion cocktail comprises an aqueous solution of (1) a water-soluble, predominantly lower molecular weight, low sweetness carbohydrate, (2) a polyhydric alcohol, (3) salt, (4) a non-inorganic sweetness depressant agent, and (5) nisin-containing whey derived from a nisin-producing culture; (b) collecting the vegetables and removing excess antimicrobial infusion cocktail; (c) drying the collected vegetables to a water activity of about 0.5 to about 0.9 to form the intermediate moisture vegetables; and (d) packaging the intermediate moisture vegetables.
Although these methods can provide improved intermediate moisture vegetables, there remains a need for even further improvements. The present method provides such improvements. Indeed, the present method allows the preparation of intermediate moisture vegetables which are shelf stable and which have significantly improved organoleptic properties. In taste tests, the present intermediate moisture vegetables were often ranked as good as or even better than cooked frozen vegetables, including high quality individually quick frozen (IQF vegetables).